Boosting Alkaline Seawater Oxidation of CoFe-layered Double Hydroxide Nanosheet Array by Cr Doping.

The pursuit of stable and efficient electrocatalysts toward seawater oxidation is of great interest, yet it poses considerable challenges. Herein, the utilization of Cr-doped CoFe-layered double hydroxide nanosheet array is reported on nickel-foam (Cr-CoFe-LDH/NF) as an efficient electrocatalyst for oxygen evolution reaction in alkaline seawater. The Cr-CoFe-LDH/NF catalyst can achieve current densities of 500 and 1000 mA cm -2 with remarkably low overpotentials of only 334 and 369 mV, respectively. Furthermore, it maintains at least 100 h stability when operated at 500 mA cm-2.

High-Performance Electrocatalytic Reduction of Nitrite to Ammonia under Ambient Conditions on a FeP@TiO2 Nanoribbon Array.

Electrochemical nitrite (NO2-) reduction is recognized as a promising strategy for synthesizing valuable ammonia (NH3) and degrading NO2- pollutants in wastewater. The six-electron process for the NO2- reduction reaction is complex and necessitates a highly selective and stable electrocatalyst for efficient conversion of NO2- to NH3. Herein, a FeP nanoparticle-decorated TiO2 nanoribbon array on a titanium plate (FeP@TiO2/TP) is proposed as an efficient catalyst for NH3 production under ambient conditions. In 0.1 M NaOH with 0.1 M NO2-, such a FeP@TiO2/TP affords a large NH3 yield of 346.6 µmol h-1 cm-2 and a high Faradaic efficiency of 97.1%. Additionally, it demonstrates excellent stability and durability during long-term cycling tests and electrolysis experiments.

NiFe Layered-Double-Hydroxide Nanosheet Arrays on Graphite Felt: A 3D Electrocatalyst for Highly Efficient Water Oxidation in Alkaline Media.

It is of great importance to rationally design and develop earth-abundant nanocatalysts for high-efficiency water electrolysis. Herein, NiFe layered double hydroxide was in situ grown hydrothermally on a 3D graphite felt (NiFe LDH/GF) as a high-efficiency catalyst in facilitating the oxygen evolution reaction (OER). In 1.0 M KOH, NiFe LDH/GF requires a low overpotential of 214 mV to deliver a geometric current density of 50 mA cm-2 (η50 mA cm-2 = 214 mV), surpassing that NiFe LDH supported on a 2D graphite paper (NiFe LDH/GP; η50 mA cm-2 = 301 mV). More importantly, NiFe LDH/GF shows good durability at 50 mA cm-2 within 50 h of OER catalysis testing and delivers a faradaic efficiency of nearly 100% in the electrocatalysis of OER.

Honeycomb Carbon Nanofibers: A Superhydrophilic O2 -Entrapping Electrocatalyst Enables Ultrahigh Mass Activity for the Two-Electron Oxygen Reduction Reaction.

Electrocatalytic two-electron oxygen reduction has emerged as a promising alternative to the energy- and waste-intensive anthraquinone process for distributed H2 O2 production. This process, however, suffers from strong competition from the four-electron pathway leading to low H2 O2 selectivity. Herein, we report using a superhydrophilic O2 -entrapping electrocatalyst to enable superb two-electron oxygen reduction electrocatalysis. The honeycomb carbon nanofibers (HCNFs) are robust and capable of achieving a high H2 O2 selectivity of 97.3 %, much higher than that of its solid carbon nanofiber counterpart. Impressively, this catalyst achieves an ultrahigh mass activity of up to 220 A g-1 , surpassing all other catalysts for two-electron oxygen reduction reaction. The superhydrophilic porous carbon skeleton with rich oxygenated functional groups facilitates efficient electron transfer and better wetting of the catalyst by the electrolyte, and the interconnected cavities allow for more effective entrapping of the gas bubbles. The catalytic mechanism is further revealed by in situ Raman analysis and density functional theory calculations.

High-Performance Electrochemical NO Reduction into NH3 by MoS2 Nanosheet.

Electrochemical reduction of NO not only offers an attractive alternative to the Haber-Bosch process for ambient NH3 production but mitigates the human-caused unbalance of nitrogen cycle. Herein, we report that MoS2 nanosheet on graphite felt (MoS2 /GF) acts as an efficient and robust 3D electrocatalyst for NO-to-NH3 conversion. In acidic electrolyte, such MoS2 /GF attains a maximal Faradaic efficiency of 76.6 % and a large NH3 yield of up to 99.6 µmol cm-2 h-1 . Using MoS2 nanosheet-loaded carbon paper as the cathode, a proof-of-concept device of Zn-NO battery was assembled to deliver a discharge power density of 1.04 mW cm-2 and an NH3 yield of 411.8 µg h-1 mgcat. -1 . Calculations reveal that the positively charged Mo-edge sites facilitate NO adsorption/activation via an acceptance-donation mechanism and disfavor the binding of protons and the coupling of N-N bond.

Biomimetic Assembly of a Polydopamine Layer on Graphene as an Electron Gate for Fluorescent MicroRNA Detection in Living Cells.

A novel strategy was developed for microRNA detection based on the fluorescence quenching of polydopamine (PDA)-coated reduced graphene oxide (RGO) nanosheets (RGO@PDA). Compared with graphene oxide (GO), the reduction of GO and modification of the surface of RGO by PDA not only improve the stability, dispersity, biocompatibility, and cellular uptake without degeneration of the unique electronic properties of graphene, but also add an electron gate for harvesting electrons, as well as enabling efficient and forward electron transfer to avoid unwanted electron transfer and realize highly sensitive miRNA detection; thus a lower detection limit can be achieved in this sensing system. Remarkably, nanoprobes consisting of RGO@PDA and fluorescein-labeled single-stranded DNA can naturally enter cancer cells without the aid of transfection agents, as well as resisting enzymatic lysis and showing almost no effect on the cell viability. More importantly, intense and time-dependent fluorescence responses were observed from the important tumor marker microRNA-21 (miR-21) in living cells; thus suggesting that the proposed sensing platform shows great promise for applications in disease diagnosis and fundamental research into biochemistry.

Highly Selective Electrochemical Reduction of CO2 to Alcohols on an FeP Nanoarray.

Electrochemical reduction of CO2 into various chemicals and fuels provides an attractive pathway for environmental and energy sustainability. It is now shown that a FeP nanoarray on Ti mesh (FeP NA/TM) acts as an efficient 3D catalyst electrode for the CO2 reduction reaction to convert CO2 into alcohols with high selectivity. In 0.5 m KHCO3 , such FeP NA/TM is capable of achieving a high Faradaic efficiency (FE CH 3 OH ) up to 80.2 %, with a total FE CH 3 OH + C 2 H 5 OH of 94.3 % at -0.20 V vs. reversible hydrogen electrode. Density functional theory calculations reveal that the FeP(211) surface significantly promotes the adsorption and reduction of CO2 toward CH3 OH owing to the synergistic effect of two adjacent Fe atoms, and the potential-determining step is the hydrogenation process of *CO.

A MoN nanosheet array supported on carbon cloth as an efficient electrochemical sensor for nitrite detection.

Nitrite, widely found in the environment and the food industry, poses a great threat to human health because of its potential toxicity, and its detection is highly important. We report that a MoN nanosheet array on carbon cloth (MoN NA/CC) behaves as an efficient catalyst for nitrite reduction in neutral solution. As a nitrite sensor, this MoN NA/CC offers a wide linear range from 1 µM to 5 mM and a low detection limit of 3 nM (S/N = 3), with a high sensitivity of 4319 µA mM-1 cm-2 and long-term stability and reproducibility.

Greatly Improving Electrochemical N2 Reduction over TiO2 Nanoparticles by Iron Doping.

Titanium-based catalysts are needed to achieve electrocatalytic N2 reduction to NH3 with a large NH3 yield and a high Faradaic efficiency (FE). One of the cheapest and most abundant metals on earth, iron, is an effective dopant for greatly improving the nitrogen reduction reaction (NRR) performance of TiO2 nanoparticles in ambient N2 -to-NH3 conversion. In 0.5 m LiClO4 , Fe-doped TiO2 catalyst attains a high FE of 25.6 % and a large NH3 yield of 25.47 µg h-1 mgcat -1 at -0.40 V versus a reversible hydrogen electrode. This performance compares favorably to those of all previously reported titanium- and iron-based NRR electrocatalysts in aqueous media. The catalytic mechanism is further probed with theoretical calculations.

Boosting electrocatalytic performance via electronic structure regulation for acidic oxygen evolution.

High-purity hydrogen produced by water electrolysis has become a sustainable energy carrier. Due to the corrosive environments and strong oxidizing working conditions, the main challenge faced by acidic water oxidation is the decrease in the activity and stability of anodic electrocatalysts. To address this issue, efficient strategies have been developed to design electrocatalysts toward acidic OER with excellent intrinsic performance. Electronic structure modification achieved through defect engineering, doping, alloying, atomic arrangement, surface reconstruction, and constructing metal-support interactions provides an effective means to boost OER. Based on introducing OER mechanism commonly present in acidic environments, this review comprehensively summarizes the effective strategies for regulating the electronic structure to boost the activity and stability of catalytic materials. Finally, several promising research directions are discussed to inspire the design and synthesis of high-performance acidic OER electrocatalysts.

Sn-based electrocatalysts for electrochemical CO2 reduction.

Electrochemical CO2 reduction into value-added chemicals represents an attractive and promising approach to capitalize on the abundant CO2 present in the atmosphere. This reaction, however, is hampered by low energy efficiency and selectivity owing to competition from hydrogen evolution reaction and multiple-electron transfer processes. Therefore, there is a pressing need to develop efficient yet cost-effective electrocatalysts to facilitate practical applications. Sn-based electrocatalysts have gained increasing attention in this active field due to their outstanding merits such as abundance, non-toxicity, and environmental friendliness. This review provides a comprehensive overview of recent advances in Sn-based catalysts for the CO2 reduction reaction (CO2RR), beginning with a brief introduction to the CO2RR mechanism. Subsequently, the CO2RR performance of various Sn-based catalysts with different structures is discussed. The article concludes by addressing the existing challenges and offering personal perspectives on the future prospects in this exciting research area.

Fe3O4 nanoparticle-decorated 3D pinewood-derived carbon for high-efficiency electrochemical nitrate reduction to ammonia.

Electrochemical nitrate (NO3-) reduction is a sustainable pathway for ambient ammonia (NH3) synthesis while eliminating NO3- pollutants in water. However, the NO3- reduction reaction (NO3-RR) involves a complicated eight-electron transfer process, which needs highly selective and efficient electrocatalysts. This work describes the synthesis of Fe3O4 nanoparticle-decorated 3D pinewood-derived carbon (Fe3O4/PC) as a high-efficiency catalyst for the electroreduction of NO3- to NH3 at ambient reaction conditions. When tested in 0.1 M NaOH containing 0.1 M NO3-, the Fe3O4/PC obtains a large NH3 yield of 394.8 µmol h-1 cm-2 and high faradaic efficiency (FE) of 91.6% at -0.4 V. Significantly, Fe3O4/PC also delivers high stability.

3D cauliflower-like Ni foam: a high-efficiency electrocatalyst for ammonia production via nitrite reduction.

A 3D cauliflower-like Ni foam on titanium plate (Ni foam/TP) shows high electrocatalytic performance for ambient ammonia (NH3) synthesis via nitrite (NO2-) reduction. In 0.1 M phosphate-buffered saline solution with 0.1 M NO2-, such Ni foam/TP attains a high NH3 Faradaic efficiency (FE) of 95.9% and a large NH3 yield of 742.7 µmol h-1 cm-2 at -0.8 V. Its Zn-NO2- battery offers a high power density of 6.2 mW cm-2 and an NH3 FE of 90.1%.

High-Efficiency Electroreduction of Nitrite to Ammonia on Ni Nanoparticles Strutted 3D Honeycomb-Like Porous Carbon Framework.

Electroreduction of nitrite (NO2 - ) to ammonia (NH3 ) provides a sustainable approach to yield NH3 , whilst eliminating NO2 - contaminants. In this study, Ni nanoparticles strutted 3D honeycomb-like porous carbon framework (Ni@HPCF) is fabricated as a high-efficiency electrocatalyst for selective reduction of NO2 - to NH3 . In 0.1 M NaOH with NO2 - , such Ni@HPCF electrode obtains a significant NH3 yield of 12.04 mg h-1 mgcat. -1 and a Faradaic efficiency of 95.1 %. Furthermore, it exhibits good long-term electrolysis stability.

Economical, green synthesis of fluorescent carbon nanoparticles and their use as probes for sensitive and selective detection of mercury(II) ions.

The present article reports on a simple, economical, and green preparative strategy toward water-soluble, fluorescent carbon nanoparticles (CPs) with a quantum yield of approximately 6.9% by hydrothermal process using low cost wastes of pomelo peel as a carbon source for the first time. We further explore the use of such CPs as probes for a fluorescent Hg(2+) detection application, which is based on Hg(2+)-induced fluorescence quenching of CPs. This sensing system exhibits excellent sensitivity and selectivity toward Hg(2+), and a detection limit as low as 0.23 nM is achieved. The practical use of this system for Hg(2+) determination in lake water samples is also demonstrated successfully.

Synthesis and study of plasmon-induced carrier behavior at Ag/TiO2 nanowires.

Nanocomposites of Ag/TiO(2) nanowires with enhanced photoelectrochemical performance have been prepared by a facile solvothermal synthesis of TiO(2) nanowires and subsequent photoreduction of Ag(+) ions to Ag nanoparticles (AgNPs) on the TiO(2) nanowires. The as-prepared nanocomposites exhibited significantly improved cathodic photocurrent responses under visible-light illumination, which is attributed to the local electric field enhancement of plasmon resonance effect near the TiO(2) surface rather than by the direct transfer of charge between the two materials. The visible-light-driven photocatalytic performance of these nanocomposites in the degradation of methylene blue dye was also studied, and the observed improvement in photocatalytic activity is associated with the extended light absorption range and efficient charge separation due to surface plasmon resonance effect of AgNPs.

Synthesis of Ag nanoparticle-decorated 2,4,6-tris(2-pyridyl)-1,3,5-triazine nanobelts and their application for H2O2 and glucose detection.

The present paper reports on the first preparation of 2,4,6-tris(2-pyridyl)-1,3,5-triazine nanobelts (TPTNBs) by adjusting the pH value of the solution and the subsequent synthesis of Ag nanoparticle (AgNP)-decorated TPTNBs (AgNP-TPTNBs) by mixing an aqueous AgNO(3) solution with preformed TPTNBs without use of any external reducing agent. It is found that the resultant AgNP-TPTNBs exhibit notable catalytic performance for H(2)O(2) reduction. A glucose biosensor was fabricated by immobilizing glucose oxidase (GOD) onto a AgNP-TPTNBs-modified glassy carbon electrode (GCE) for glucose detection. The constructed glucose sensor has a wide linear response range from 3 mM to 20 mM (r: 0.999) with a detection limit of 190 µM. It is further shown that this glucose biosensor can be used for glucose detection in human blood serum.

Novel application of CoFe layered double hydroxide nanoplates for colorimetric detection of H(2)O(2) and glucose.

The present communication demonstrates the proof of concept of using CoFe layered double hydroxide (CoFe-LDHs) nanoplates as an effective peroxidase mimetic to catalyze the oxidation of peroxidase substrate 3,3',5,5'-tetramethylbenzidine in the presence of H(2)O(2) to produce a blue solution. We further demonstrate successfully CoFe-LDHs nanoplate-based colorimetric assay to detect H(2)O(2) and glucose.

Environmentally friendly, one-pot synthesis of Ag nanoparticle-decorated reduced graphene oxide composites and their application to photocurrent generation.

In this paper, we develop an environmentally friendly, one-pot strategy toward rapid preparation of Ag nanoparticle-decorated reducd graphene oxide (AgNPs/rGO) composites by heating the mixture of GO and AgNO(3) aqueous solution in the presence of sodium hydroxide at 80 °C under stirring. The reaction was accomplished within a short period of 10 min without extra reducing agent. As-synthesized AgNPs/rGO composites have been successfully applied in photocurrent generation in the visible spectral region.

Anchoring gold nanoparticles on graphene nanosheets functionalized with cationic polyelectrolyte: a novel catalyst for 4-nitrophenol reduction.

In this paper, a stable aqueous dispersion of graphene nanosheets (GNs) has been prepared by chemical reduction of graphene oxide (GO) with hydrazine hydrate in the presence of poly [(2-ethyldimethylammonioethyl methacrylate ethyl sulfate)-co-(1-vinylpyrrolidone)] (PQ11). Taking advantages of the fact that PQ11 is a positively charged polymer exhibiting reducing ability, we further demonstrated the subsequent decoration of GN with gold nanoparticals (AuNPs) by in-situ chemical reduction of HAuCl4. It was found that such nanocomposites exhibit good catalytic activity toward 4-nitrophenol (4-NP) reduction and the GN supports also enhance the catalytic activity via a synergistic effect.